Calling a Dll

[DaoK]

Hello!
I made a dll :

#include "MYDLL.h"
__declspec( dllexport ) int doubleInt(int iNumber)
{
    return (iNumber * 2);
} 

and a .DEF

LIBRARY        MYDLL
   DESCRIPTION    "Simply double an integer"
   EXPORTS
            doubleInt  @1

but now that's what I just found in some thread here but that doesn't work and I know that I miss something but I really do not have a clue how to call my DLL in an other C++ project

Here is what I got :

#include <iostream>

//Prototype
void LoadDll(void);

void main(void)
{
    LoadDll();
}//End main

void LoadDll(void)
{
    HMODULE hDLL = LoadLibrary("MYDLL");
    if (hDLL)
        MYFUNC function = (MYFUNC)GetProcAddress(hDLL, "MyFunction");
    else
        std::cout << "Error loading DLL";
}//End LoadDll 

Any one can help me ?

[DaoK]

Here is all error :

error C2065: 'HMODULE' : undeclared identifier

error C2146: syntax error : missing ';' before identifier 'hDLL'

error C2065: 'hDLL' : undeclared identifier

error C2065: 'LoadLibrary' : undeclared identifier

error C2065: 'MYFUNC' : undeclared identifier

error C2146: syntax error : missing ';' before identifier 'function'

error C2065: 'function' : undeclared identifier

error C2146: syntax error : missing ';' before identifier 'GetProcAddress'

error C2065: 'GetProcAddress' : undeclared identifier

error C2181: illegal else without matching if

[abdul]

Try this...

Your DLL source file:

#include "MYDLL.h"
int __declspec( dllexport ) doubleInt(int iNumber)
{
    return (iNumber * 2);
} 

Your .DEF file:

LIBRARY        "MYDLL.dll"
   DESCRIPTION    "Simply double an integer"
   EXPORTS
            doubleInt 

Almost make sure your DLL header file is also right.

Now, the code you're testing your DLL with:

#include <iostream>
#include <windows.h> 'Must if you're using LoadLibrary, etc
//Prototype
void LoadDll(void);
//Must declare a function pointer type you want
typedef void (*MYFUNCTION)(int);
void main(void)
{
    LoadDll();
}//End main

void LoadDll(void)
{
'HMODULE is old.  Use HINSTANCE instead
    HINSTANCE hDLL = LoadLibrary("MYDLL.dll"); 'Extension
    if (hDLL)
      MYFUNCTION myfunc= (MYFUNCTION)GetProcAddress(hDLL, "MyFunction"); //Shouldn't it be doubleInt?
//You can free the DLL here just for performance
//FreeLibrary(hDLL);
    else
        std::cout << "Error loading DLL";
}//End LoadDll 

Make sure the path to DLL is correct and naming of all the files is also correct.
Might be some typos in the above code though.

[DaoK]

Yes but how can i use the doubleInt function ?

I tryed that in the main :

void main(void)
{
    LoadDll();
    int a = 5;
    a = myfunc(a);
    std::cout << a;
}//End main 

but that doesn't work

[parksie]

You have to assign it to a function pointer, then call through the pointer:

(*myfunc)(a);

[DaoK]

Why that doesn't work ?

#include <iostream>
#include <windows.h> //Must if you're using LoadLibrary, etc
//Prototype
void LoadDll(void);
//Must declare a function pointer type you want
typedef int (*MYFUNCTION)(int);
void main(void)
{
    LoadDll();
    int a = 5;
    a = (*myfunc)(a);
    std::cout << a;
}//End main

void LoadDll(void)
{
    HINSTANCE hDLL = LoadLibrary("deuxDll.dll");
    if (hDLL)
      MYFUNCTION myfunc = (MYFUNCTION)GetProcAddress(hDLL, "doubleInt");
//You can free the DLL here just for performance
//FreeLibrary(hDLL);
    else
        std::cout << "Error loading DLL";
}//End LoadDll 

Error:

error C2065: 'myfunc' : undeclared identifier

error C2100: illegal indirection

[abdul]

Declare "myfunc" on the top of your code.

#include <iostream>
#include <windows.h> //Must if you're using LoadLibrary, etc
//Prototype
void LoadDll(void);
//Must declare a function pointer type you want
typedef int (*MYFUNCTION)(int);
MYFUNCTION myfunc; //Declare it
void main(void)
{
    LoadDll();
    int a = 5;
    a = (*myfunc)(a);
    std::cout << a;
}//End main

void LoadDll(void)
{
    HINSTANCE hDLL = LoadLibrary("deuxDll.dll");
    if (hDLL)
      myfunc = (MYFUNCTION)GetProcAddress(hDLL, "doubleInt");
//You can free the DLL here just for performance
//FreeLibrary(hDLL);
    else
        std::cout << "Error loading DLL";
}//End LoadDll 

[DaoK]

Ok but I have a speacial msgbox with an error when I execute, maybe I have an error when is time to load the DLL in the pointer.

...thx for debugging me I appreciate.

[DaoK]

When I pass the program in debug I have RED hex code in the debugger screen... I think I do something wrong

[DaoK]

Ok I found out what was wrong THX all!!!!

[parksie]

Originally posted by DaoK
When I pass the program in debug I have RED hex code in the debugger screen... I think I do something wrong

It's highlighted in red if the value's changed


Everything working now?